Semiconductor translating device



1954 J. v. DOMALESKI EIAL 10 SEMICONDUCTOR TRANSLATING DEVICE Filed NOV.50, 950

FIG. 2

J. V. DOHALE'SK/ INVENTORS E.L. GARTLA/VD J.J. KLEIMACK BYIW ATTORNEYPatented Aug. 31, 1954 UNITED STATES PATENT OFFICE SEMICONDUCTORTRANSLATING DEVICE corporation of New York Application November 30,1950, Serial No. 198,294

13 Claims.

This invention relates to translating devices and more particularly totranslating devices including a body of semiconductive material on asurface of which one or more point contacts bear, and to methods ofmanufacture of such devices,

One form of translating device of the type to which this inventionpertains comprising a block of semiconductive material mounted on aconductive backing member, termed the base, and a pair of closely spacedlimited area contacts which make asymmetric connections with the surfaceof the conductive body is disclosed in Patent 2,524,035 of John Bardeenand Walter H. Brattain issued October 3, 1950. The limited area contactstermed the emitter and collector are spaced for mutual influence and inone form of the device are formed of fine wire.

Since the operation of such devices is dependent upon the accuracy ofspacing between the emitter and collector, heretofore it has been foundnecessary to mount the units in rather bulky assemblies which providemechanical rug' gedness. Such assemblies are space consuming anddifficult to manufacture readily in quantity.

One object of this invention is to simplify the structure andmanufacture of translating devices of the above-noted type. Morespecific objects of this invention are to reduce the size of translatingdevices and also their cost by reducing the amount of material employedand eliminating the precision work and the number ofsteps necessary intheir manufacture.

In accordance with one feature of this invention, a semiconductortranslating device of the eneral construction described above is encasedin a bead of insulating material.

More specifically, in accordance with one feature of this invention thecontact or contacts and the semiconductor body are fabricated in aunitary assembly and are secured and protected in prescribed relationshiby an encasin bead or capsule of insulating material. Contacts may be soarranged and the casing material so applied to the assembly that theportion of the bead or capsule wherein the contacts engage thesemiconductor surface is hollow. The contacts are provided with springsections within the cavity thereby insuring the maintenance of a springpressure biasing the contacts toward the semiconductor throughout thelife of the device without the danger of losing contact or shiftin theposition of the contacts due to mechanical strains applied to the beador to expansion and contraction of the bead with temperature.

The above-noted and other objects and fea- 2 turcs of this inventionwill be understood more clearly and fully from the following detaileddescription when read in conjunction with the accompanying drawings, inwhich:

Fig. 1 is a sectioned front elevation of a threeelectrode translatingdevice illustrative of one embodiment of thi invention; and

Fig. 2 is a sectioned side elevation of the device of Fig. 1 taken alongthe line 2-2.

Referring now to the drawings, Figs. 1 and 2 show a three-electrodetranslating device H includin a semioonductive body l2 of germanium orsilicon secured to a base member [3 by an ohmic connection, and having apair of point contacts i l and i5 engaging its other surface to providean emitter and a collector. The contacts are of spring material;favorable results have been obtained with a beryllium copper emit er anda Phosphor bronze collector. This assembly is surrounded by a bead llwhich may be of a styrene-polyester casting resin and which contains acavity in the region l8 surrounding the point contacts and theassociated semiconductor surface. Situated in this cavity it are thespring sections It and 26 of the point contaots. These spring sectionsare biased in com pression toward the semiconductor so that through alltemperature cycles or other mechanical stresses to which the unit willbe subjected during its operation the points will be stable mechanially. While the cavity 18 of the bead might conveniently be left empty,it has been found that the surface of the semiconductor can be readilyprotected from contamination and that the hollow can be maintained andcontrolled in the bead by filling the region with a material which stayssoft at any operating temperature to which the device is to besubjected, which will not contaminate the wafer surface, and which will.protect the surface from contamination by any of the other materialsemployed. These requirements are fulfilled by materials such as a highpurity paraffin or polyethylene polyisobutylone.

In order to further simplify the construction of the device, the ends ofthe contact wires 22 and 23 are utilized as terminals. These wires maybe bent around the surface of the bead I! and secured with an outerlayerof beading material (not shown), although they are anchored to the beadsufficiently by the bend 3| embedded therein.

The illustrative unit can be constructed by forming a spade end 25 on asuitable conductive base l3, for example a 20-mil copper wire. The

spade end 25 is then bent at 90 degrees to the axis of the wire and theportion 27 near its end is bent in the direction of the axis to form anoffset. Alternatively, a flat conductive strip can be employed as thebase I3 and can be bent as above or otherwise to form a pocket in whichthe semiconductive wafer can be mounted, this strip can be copper 50mils wide and 5 to mils thick. A semiconductive Wafer l2 of silicon orgermanium 25 mils square is then polished mechanically on both majorsurfaces, and one surface is tinned and soldered or welded to theportion of the spade end 25 on the base 13 extending at 90 degrees toits axis. The other major surface is then etched, for example asdisclosed in the application of R. D. Heidenreich, Serial No. 164,303filed May 25, 1950, in an etchant comprising 15 parts of acetic acid, 25parts of nitric acid, 15 parts of 48 per cent hydrofluoric acid and 1part of liquid bromine. This etch is followed by a rinse. The order ofthis operation may be re versed and the chemical polish completed priorto mounting the Wafer.

The wafer-base assembly is then mounted in a suitable jig. A pair ofpoint contacts [4 and I5, which may be formed from 5-mil phosphor bronzewire having sheared ends, are secured in a jig which maintains thespacing of their ends at from 2 to 5 mils. These wires and their jig areadvanced to contact the polished and etched surface. These contacts areeach provided with a section l9 and adjacent the point suitable forproviding spring action and a means for mechanically securing them inthe bead material. An S-shaped portion adjacent the pointed ends isemployed to obtain these desired characteristics. A globule ofpolyethylene polyisobutylene or some other material which will remainsoft at the operating temperatures of the unit is applied to theassembly to encompass the wafer point and one bend of the S-shapedportion of each contact wire adjacent the point. This globule, whichprovides a means of attaining a cavity within the encasing bead, issupported in position by the pocket formed by the ofiset portion 2? ofthe spade end of the base in cooperation with the contact wires. A crust28 is formed over the globule by applying a quick drying lacquer theretoin a thin layer. This lacquer should be of a type that is notdetrimental to the material of the globule and is tough enough to form asupporting crust over it; a vinyl lacquer may be used for this purpose.A bead ii of the encasing material is then formed over the shaft of thebase contact l3, over the globule forming cavity I8, and over the upperbends 30 and 3| of the S-shaped portions of the point contacts toencompass the entire assembly. The encasement of the upper bends of thecontact wires by the beading material serves to secure them rigidly inplace.

A suitable beading material is a styrene-polyester casting resin, forexample that identified as Selectron, applied either in the clear stateor with a silica loading to increase the heat dissipation from theoperating elements. A successful beading material has been Selectronloaded 45 per cent with silica. This coating is then cured for exampleby heating to from 80 C. to 120 C. for one hour after which the pointcontact wires may be bent around the bead and a second application ofthe beading material applied and cured to insure a rugged mechanicalassembly.

Such a construction, as set forth above, is

4 small, electrically and mechanically rugged and is extremely wellsuited for package circuits which are potted. The units may beconstructed with a single point contact and function either as a pointcontact rectifier or with a suitable choice of translucent encasingmaterial as a photosensitive translating device of the type disclosed inJ. N. Shive application Serial No. 110,684, filed August 17, 1949. Wherephoto effects are undesirable it may be found advantageous to employbeading compositions which are opaque to light.

t is to be understood that the above-described arrangements areillustrative of the application of the principles of this invention andnumerous other arrangements may be devised by those skilled in the artWithout departing from its spirit and scope.

What is claimed is:

1. A semiconductive translating device comprising a semiconductive body,a first electrode making contact to said body, a second electrodesecured to said body, a seamless hollow envelope of insulating materialsurrounding said body and engaging said electrodes and securing them intheir relative positions, said envelope having a cavity which containsat least a portion of said semiconductive body and said first contact, aflexible section in said first electrode within said cavity andintermediate said envelope and said first contact, and a yieldable,nonconducting material surrounding said flexible section and fillingsaid cavity.

2. A semiconductive translating device comprising a conductive membercontaining a pocket, a semiconductive body electrically and mechanicallyconnected to said member in said pocket;

a contact to said body, a conductive lead engaging and extending fromsaid contact, a conductive lead extending from said conductive member, aseamless hollow envelope of insulating material surrounding said memberand said body and engaging a portion of said member and said leads andsecuring them in their relative positions, said envelope having a cavitypartially defined by said pocket and containing at least a portion ofsaid semiconductive body and said contact, a flexible section in saidlead intermediate said envelope and said contact and Within said cavity,and a yieldable, nonconducting material surrounding said flexiblesection and filling said cavity.

3. A semiconductive translating device comprising a semiconductive body,a first electrode making a limited area contact to said body, a secondelectrode secured to said body and making a contact thereto of greaterarea than said first contact, a seamless hollow envelope of insulatingmaterial surrounding said body and engaging said electrodes and securingthem in their relative positions, said envelope having a cavity Whichcontains at least a portion of said semiconductive body and said contactof limited area,

in the wall of said envelope to fix said wire, and a yieldable,nonconducting material surrounding said second bend and filling saidcavity.

5. A semiconductive translating device including a base, an emitter anda collector electrode comprising, a wire, a semiconductive body securedto said wire with an ohmic contact, a pair of wires of resilientmaterial, a point contact on the end of each of said resilient wiresengaging said body in critically spaced relationship, 8- shaped bends insaid resilient wires, and a bead having a cavity containing said body,said point contacts and the turn of each S-shaped bend adjacent saidcontacts, the wall of said bead securing said wire and the turn of eachs-shaped bend farthest removed from said contacts.

6. In the method of manufacturing semiconductive translating devices,the steps which comprise mounting a semiconductive body on a conductivebase, mounting a limited area contact on the body with a spring biasingit toward the body, placing a globule of material which remains softover the contact and spring, and forming a bead over the globule, thewalls of the bead securing the conductive base, the spring and thecontact.

7. In the method of manufacturing semiconductive translating devices,the steps which comprise mounting a semiconductive body on a conductivebase, mounting a limited area contact on the body with a spring biasingit toward the body, placing a globule of material which remains softover the contact and spring, coating the globule with a tough protectivelayer, and forming a bead over the globule, the walls of the beadsecuring the conductive base, the spring and the contact.

8. In the method of manufacturing semiconductive translating devices thesteps which comprise mounting a semiconductive body on a conductivebase, forming an S-shaped bend in a pointed resilient wire, mounting thepointed end of the wire with the bend in compression on a semiconductivesurface, placing a globule of material which remains soft over thecontact and the turn of the s-shaped bend adjacent the contact, andforming a bead over the globule, the walls of the bead securing theconductive base and the exposed portion of the s-shaped bend.

9. In the method of manufacturing semiconductive translating devices,the steps which comprise forming a spade end on a conductive rod,securing a semiconductive body to a portion of said spade end adjacentthe rod, bending another portion of said spade end in the direction ofthe body, mounting a pair of spring biased point contacts on said bodyin critically spaced relationship, placing a globule of material whichremains soft in the pocket formed by the bent spade end and over thecontacts, coating the globule with a tough protective layer, and forminga bead over the globule, the walls of the bead securing the conductiverod and the contacts.

10. In the method of manufacturing semiconductive translating devices,the steps which comprise mounting a semiconductive body on a conductivebase, mounting a limited area contact on the body with a spring biasingit toward the body, placing a globule of polyethylene polyiso- 6butylene over the contact and spring, coating the globule with a vinyllacquer, forming a bead. of a styrene-polyester casting resin over theglobule to secure the conductive base, the spring and contact, andcuring the bead by heating at about C. for about one hour.

11. A semiconductive translating device comprising a semiconductivebody, base, emitter and collector contacts to said body, leads extendingfrom each of said contacts, a flexible section in at least one of saidleads adjacent its respective contact, a seamless hollow envelope ofinsulating material surrounding said body, said envelope engaging andsecuring in fixed relationship at least a portion of each of said leads,said envelope having a cavity which contains at least a portion of thesemiconductive body and said flexible section of said lead and itsrespective contact to said body, and a yieldable, nonconducting materialsurrounding said flexible lead section and filling said cavity.

12. A semiconductor translating device comprising a semiconductive body,a first electrode making a limited area contact to said body, a secondelectrode secured to said body and making a contact thereto of greaterarea than said first contact, a seamless hollow envelope of resinousinsulating material surrounding said body, said envelope engaging aportion of said electrodes and said body and securing them in theirrelative positions, a bend in said first electrode embedded in saidresinous material to anchor the electrode, said envelope having a cavityencompassing that portion of said first electrode and of saidsemi-conductive body surface including said limited area contact, aflexible section in said first electrode Within said cavity, and a softprotective material for said semiconductive body filling the cavity.

13. In the method of manufacturing a semiconductive translating device,the steps which comprise securing an electrical contact to asemiconductive body, mounting a second contact on the body at a locationspaced from said contact, forming a flexible section in the lead to thesecond contact, placing a globule of material which remains in ayieldable state over the second contact and flexible lead section, andforming a continuous layer of rigid nonconductive material over theglobule, the semiconductive body, and the contacts to said body, saidrigid material securing at least a portion of the leads associated withthe contacts.

References Cited in the flle of this patent UNITED STATES PATENTS Number

